This invention specifically relates to electrophoresis used in biochemical and immunochemical experiments.
Electropheresis separates biological molecules in a mixture into individual components under the influence of electric current. In addition to others, it requires a porous physical support. At present, polymerized acrylamide is commonly used as an inert gel matrix because it offers many advantages. In several analytical as well a preparative studies, acrylamide based gel electrophoresis is used as a method of choice to separate proteins, nucleic acids and a carbohydrate complexes.
As a technique, gel electrophoresis has become very popular because, it requires only a small amount of sample for analysis, its parameters can be changed to suit different needs, and biologicals can be analyzed in native and denaturing conditions. After separation, molecules such as proteins can be fixed in gel and then stained with dye. After destaining, isolated proteins are seen as bands of color. The destained gels are then dried for handling easily, for analyzing molecular properties, and for storing.
Active and passive methods, based on dehydration, are used to preserve acrylamide gels containing stained proteins. In active methods, gel is usually dehydrated by using vacuum suction with or without applying heat. In one method, U.S. Pat. No. 4,883,597, gel placed on a polyethylene membrane is dried by applying vacuum. In another method, U.S. Pat. No. 4,020,563, acrylamide gel placed on a filter paper, is dehydrated by a combination of heat and vacuum suction. The end product is a filter paper containing a thin film of dry gel where protein pattern is seen only by reflected light. Generally, thick bands are seen clearly; but thin bands are seen with poor distinction. Other complex apparatus containing heating mechanisms are described in U.S. Pat. Nos. 4,612,710 and 4,778,778. These methods of drying are generally expensive because they require a) an apparatus to keep filter paper-gel complex air tight, b) a mechanism to heat the gel assembly, c) a pump to generate vacuum, and d) a trap for removing liquid vapors. Trap needs an effective cooling system to condense and then freeze all vapors before they pollute vacuum pump oil. Eventhough gels are dried fast, more than often, gels crack because of vacuum drawing fluid rapidly from the surface of gel.
In passive method, the amount of water is decreased by first soaking the gel in a solvent mixture such as ethyl alcohol, glycerol and water. After this treatment, the size of gel usually shrinks approximately by 10 to 15%. A passive method of drying a slab gel is described by Wallevik, K and Jensenius, J. C., in the Journal of Biochemical and Biophysical Methods, 6, (1982) 17-21. In their method, liquid is evaporated a room temperature, in open air, from both surfaces of slab gel. This is accomplished first by making cellophane-gel-cellophane sandwich and then placing it between two frames held together b metal binder clamps.
Cellophane provides transparency and also supports the gel for easy handling during drying. Also, cellophane b making acrylamide attach to its surface, minimizes the appearance of cracks in the gel. Basically, cellophane is nothing more than thin flat gel supports. These cellophanes sheets are commonly available from most stores which sell plastic hand bags, lunch bags and other types of think plastic sheets.
Other manufacturers have described apparatus containing variations for passive method of drying gels. The gel drying system of Hoeffer Scientific Instruments contains frames and a platform. The platform fits into the opening of the lower frame. This provides a stage for assembling gel-cellophane sandwich directly on the frame. The gel dryer of Kem-En-Tec has legs in the frame which support the unit stay horizontal above the flat surface of bench. The apparatus manufactured by Novel Experimental Technology U.S. Pat. Nos. 5,440,822 and 5,572,802, contains a base unit whose flat top fits into the opening of lower frame for assembling gel-cellophane sandwich. The trough of base collects any droops of liquid if oozes out during the assembly. Frames and gel sandwich complex is held together by plastic clips. The complete assembly stands erect on the legs present on one end of both frames.
Each of the gel drying apparatus of the prior art, along with other features, is aimed to enhance uniform drying of the gel which is flanked by cellophane sheets. However, the disadvantages are that each unit has several individual parts such as frames, plates, base, metal clamps or plastic clips which have to be assembled and disassembled after every use. Metal clamps rust because of contact with various reagents. Plastic clips are hard to push in to place because of increase thickness of the assembled product. At the end of drying, it is equally hard to remove tightly placed clips because of lack of proper grip. After drying, the surfaces of plate, frame and gel-cellophane sandwich stay tightly stuck to one another. To separate them, normally a sharp tool such as a knife, chisel or a razor blade is used to ply open. Repeated use of these sharp tools causes permanent damage to the surfaces of frames and often cuts the gel cellophane sandwich.
From the above described information, it is clear that there is a need for a gel dryer, which remains as one entity with no requirements for assembly and disassembly of separate parts either before or after use. Such a unit because of localization of various parts, eliminates orientation and alignment of frames which otherwise is needed for assembling gel-cellophane sandwich in the unit. It should incorporate other provisions such as a platform without requiring a separate stage, a mechanism to hold tightly the gel sandwich between frames without requiring plastic clips or metal clamps, a structural feature to separate frames as well as dry gel without needing an additional tool, and a system to make the unit stand on its components so that gel can dry either from one surface or from both surfaces. Such a unit is described in this invention. Any liquid that oozes out during the assembly can be removed easily by wiping the unit with a disposable paper towel.